With the advent of remote actuation of valve units by computer or manual control, there is a need to prevent operation of such valve units during repair and maintenance thereof. Chemical and petrochemical plants frequently require isolation of portions of the pipeline to service the pipeline or adjust the pipeline system. Locking out the remotely controlled valve means in a closed position within the pipeline allows for safe maintenance operations without having to shut down the entire system.
Likewise, silo or grain elevators frequently need to be entered by personnel for maintenance reasons. The operator of such a facility may not know that maintenance personnel is in the silo and could easily fill the silo with whatever product is normally stored therein. The maintenance workmen would then be inundated by this product within the silo. If the blower or conveyor for discharging material were equipped with an appropriate lockout device, no product could be moved and the problem would be avoided.
Gas, water and oil pipelines use automatic valves and pumps for distributing product throughout their respective systems. When a branch of any system needs to be worked on, the valve, pump or compressor supplying the pipeline branch needs to be isolated so that it cannot be accidentally activated from a terminal remotely located from the site of the pipeline branch. In this particular situation, it is imperative that such a mechanical lockout capability be made available because modern telemetry permits actuation of the valves, pumps or compressors at distances hundreds of miles away from the controller. Thus, an action might go unnoticed until well after a disaster has occurred along a particular pipeline.
Furthermore, large high voltage electrical switches for power distribution systems are remotely actuated from central control rooms. If these switches could be locked out with a mechanical device, work could then be done on branch lines with complete safety because any control signals from the remotely located control room could be overridden by a sound mechanical clip configuration.
Short of shutting down a process or placing redundant manual valves on either side of a remotely controlled automatic valve, it has been unsafe to open a pipeline or vessel while the particular process taking place in the transmission line was in operation. Similarly, pumps, blowers, conveyors and other devices actuated by rotation of a shaft member have made safe isolation of parts or sections impractical. These devices share several points in common. First they are either electrically, pneumatically or hydraulically powered and are actuated at some remote location. Second, they involve rotation to provide an action which is not desired for safe work. A physical mechanical restraint would prevent action or operation of the rotatable member thereby locking the system into a desired operational condition.
Reliable electrical isolation is not always possible due to the growth space design of an operational system. In the improvement of a system, space may not permit lockable manual valves to be installed on either side of the automatic valve. Furthermore, cost may be prohibitive for automating the system to automatically close down under maintenance conditions.
Known lockout clips found in the prior art are related particularly to manually operated valve systems. U.S. Pat. 441,190; 3,540,481; and 3,741,519 disclose various spring-loaded lockout clips and pins for manually operated valves. With the disclosed clips, the manually operated valves are fixed in place once the spring-loaded pin is set within the detent formed in the respective valve stem configuration.
U.S. Pat. Nos. 1,450,861 and 3,560,130 disclose various types of manually displaced pins that extend through a stem configuration of respective manually operated valves.
U.S. Pat. Nos. 988,378; 1,322,721; and 1,444,899 show various types of U-shaped or collar type clip members for preventing the accidental rotation of the disclosed manually operated valve structure. No mechanical lockout clip devices are found in the prior art for securing automatically remote controlled valve units disposed in either an open or closed position within a transmission line.